Frame data for attacks out of shield are calculated as follows:
• Up-B, U-Smash can be used immediately out of shield.
• Aerials add a 3 frame jumpsquat to the startup (can jump immediately out of shield).
• Grabs out of shield add 4 frames to startup.
• Dash attacks add 11 frames required to drop shield and an extra 1 frame to begin the dash.
• All other options add 11 frames needed to drop shield to startup.

Use the site to see what moves you can use to punish an opponent's move that hit your shield.
Also, you can see which of your moves are unpunishable or only lightly punishable by your opponent on shield.
Warning: Even though a move can punish a blocked attack based on frame data, it's possible
that the spacing makes the attack unpunishable through whiffing or being too far away.

F.A.Q.
What moves are considered punishable?
A move on shield is listed as punishable
by a move out of shield if the least negative
frame disadvantage is still enough for the
out of shield option to start (the negative
number is bigger than the positive number).
In other words, if you can hit the opponent
with the move while they are still in lag from the attack.

What is 'Rapid Finisher'?
The rapid finisher of a jab.

Aren't there some missing out of shield options?
Aerial specials and specials after dropping
shield are not included, to simplify options
and due to difficulty labeling the many special moves, sorry :(

What out of shield options are included?
All aerials, smash attacks, tilts, z-airs, grab, and up specials.

Are there some missing attacks on shield?
Attacks that put you in free fall like Mario's
Up-B are not covered, as you can generally
use your imagination to punish :)